ORGANS OF REPRODUCTION. 343 



endosperm, and the former perisperm. Both endosperm and 

 perisperm may be seen in the Nymphoea {Jig. 734), &c. The 

 general name of perisperm or albumen will be 

 principally used here, without reference to its 

 origin. From the above considerations, it will 

 be evident, that the nucleus of the seed may 

 either consist of the embryo alone, as in the 

 Wallflower, the Bean, the Pea {Jig. 725), which 

 is alone essential to it: or of the embryo en- 

 closed in albumen or perisperm, as in the 

 Pansy {Jig. 752, al). Oat {Jig. 687, a), Nymphaa 

 {Jig. 739), &c. We have two parts, therefore, 

 to describe as constituents of the nucleus, j,. ^^ vertical 

 namely, the albumen or perisperm, and the em- section of the seed 



y._-rrr» of the Wliite Wa- 



"^ All T^ ■. 1 • T tej" ^^''y- showing 



a. Albumen or Perisperm. — Those seeds which the embryo en- 

 have the embryo surrounded by a store of Sains ot^ t?e'em- 

 nourishing matter, called the albumen, are said bryo-sac orvitei- 

 to be albuminous ; while those in which it is outside"^ o^ thit 

 absent, are exalbuminous. The amount of ai- the a bumen sur- 

 bumen will in all cases be necessarily in in- i^te^men^I *^^ 

 verse proportion to the size of the embryo. 

 The term albumen will in future be chiefly employed, as it 

 is the one best understood, and so long as we recollect its 

 natm-e, the adoption of such a name can lead to no confusion. 



The cells of the albumen contain various substances, such as 

 starch, oily matters, &c., either separate or combined, and they 

 thus act as reserv^oirs of nutriment for the use of the embryo dur- 

 ing the process of germination. The varjung contents of the cells, 

 together with certain diiferences in the consistence of their 

 walls, cause the albumen to assume different appearances in the 

 ripe seed, and thus it frequently affords good characteristic 

 marks of different seeds. Thus, the albumen is described as 

 mealy, starchy, or farinaceous, when its cells are filled wiih 

 starch-grains, as in the Oat and other Cereal grains j it is said 

 to h& fleshy, as in the BarbeiTy and Heart's-ease, Avhen its walls 

 are soft and thick; when its cells contain oil-globules suspended 

 in a viscid mucilage, as in the Poppy and Coco-nut, it is oily; 

 when the cells are soft, and chiefly formed of mucilage, as in 

 the Mallow, it is mucilaginous ; or when the cells are thickened 

 by secondary deposits of a hardened nature, so that they be- 

 come of a horny consistence, as in the Vegetable Ivory Palm, 

 Coffee, &c., the albumen is described as horny or corneous. 

 These different kinds of albumen are frequently more or less 

 modified in different seeds by the admixture of one with the 

 other. 



Generally speaking the albumen presents a uniform appear- 

 ance throughout, as in the Vegetable Ivoiy ; but at other 

 z4 



